Field of the Invention
The present invention relates to an apparatus for suppressing fuel evaporative gas emission, and more particularly to control for detecting an abnormality of the apparatus for suppressing fuel evaporative gas emission.
Description of the Related Art
Conventionally, in order to prevent emission of a fuel evaporative gas evaporated in a fuel tank into the atmosphere, an apparatus for suppressing fuel evaporative gas emission is provided including: a canister mounted in a purge passage that provides communication between a fuel tank and an intake passage of an internal combustion engine; a changeover valve that opens or closes the canister to or from the atmosphere; a sealing valve that provides communication or closes between the fuel tank and the canister; and a purge solenoid valve that provides communication of and interrupts the purge passage. The apparatus for suppressing fuel evaporative gas emission opens the changeover valve and the sealing valve and closes the purge solenoid in fueling so that the fuel evaporative gas flows toward the canister, and the fuel evaporative gas is adsorbed to activated carbon provided in the canister. The apparatus for suppressing fuel evaporative gas emission opens the changeover valve and the purge solenoid valve in operation of the internal combustion engine, and discharges the fuel evaporative gas adsorbed to the activated carbon in the canister to the intake passage of the internal combustion engine to treat the fuel evaporative gas. The apparatus for suppressing fuel evaporative gas emission also detects a leak from the apparatus in order to prevent the fuel evaporative gas from leaking outside the apparatus.
For leak detection, in a conventional vehicle that travels with a drive force of an internal combustion engine, opening/closing of a changeover valve, a sealing valve, and a purge solenoid valve is controlled in operation of the internal combustion engine, a negative pressure is generated in a purge passage and a fuel tank by a negative pressure generated in an intake passage of the internal combustion engine, and a leak is determined by whether the negative pressure is held or not to detect presence or absence of a leak.
However, in a vehicle such as a plug-in hybrid vehicle that includes an internal combustion engine and also an electric motor, and travels mainly with a drive force of the electric motor, the internal combustion engine is rarely operated in order to improve fuel efficiency, and if a leak in the apparatus for suppressing fuel evaporative gas emission is to be detected in operation of the internal combustion engine, there are few opportunities for leak detection.
Thus, an apparatus for suppressing fuel evaporative gas emission provided in a vehicle with limited operation of an internal combustion engine includes a negative pressure pump that can reduce a pressure in the apparatus for suppressing fuel evaporative gas emission, and controls operation of the negative pressure pump, and opening/closing of a changeover valve, a sealing valve, and a purge solenoid valve during key-off of the vehicle to detect a leak in the apparatus for suppressing fuel evaporative gas emission.
In such an apparatus for suppressing fuel evaporative gas emission, if failures occur such as open sticking that is sticking of the changeover valve, the sealing valve, and the purge solenoid valve in an opened state, or closed sticking that is sticking thereof in a closed state, a fuel evaporative gas cannot be adsorbed to activated carbon in a canister, or cannot be discharged to an intake passage of the internal combustion engine.
Thus, for example, as failure detection of a sealing valve, there is a technique of closing a closing valve (sealing valve), and detecting open sticking of the sealing valve from presence or absence of a differential pressure between front and rear of the sealing valve when a differential pressure generation condition is satisfied such as a lapse of time, a change in temperature, a change in fuel temperature, or a change in atmospheric pressure (Japanese Patent No. 4151382).
In the apparatus for treating evaporated fuel of an internal combustion engine in Japanese Patent No. 4151382, it is determined that the sealing valve is normally operated to a closed side if the differential pressure between front and rear of the sealing valve exceeds a determination value when a differential pressure generation condition is satisfied such as a lapse of time, a change in temperature, a change in fuel temperature, or a change in atmospheric pressure, and it is determined that the sealing valve sticks to an open side, that is, the sealing valve is in open sticking if the differential pressure between front and rear of the sealing valve does not exceed the determination value.
However, since open sticking of the sealing valve is determined when a differential pressure generation condition is satisfied such as a lapse of time, a change in temperature, a change in fuel temperature, or a change in atmospheric pressure, unpreferably, open sticking of the sealing valve cannot be determined, for example, when the differential pressure generation condition is not satisfied.